An example of a molding method for producing a molding of different materials and different colors with an injection molding machine is to injection-mold one resin material into a primary side mold, feed the resultant primary molding to a secondary side mold, and injection-mold the other resin material into a gap between the cavity of the secondary side mold and the primary molding. Various types of injection molding apparatuses for two-material molding have been proposed (see Patent Documents 1 and 2).
Among such molding apparatuses, a conventional example disclosed in Patent Document 1 will be explained. An injection molding machine for two-material molding injection-molds one resin material from two sets of injection units into a primary side of two cavities defined by a mold of a movable platen, a mold of a fixed platen, and molds on both sides of a rotational platen provided between the two platens, rotates the rotational platen 180 degrees, and injects the other resin material into a secondary side cavity, whereby the two materials are integrally molded. The rotational platen is moved by a specific hydraulic cylinder. The movable platen is opened and closed by a hydraulic cylinder composed of a ram on an end of a tie bar provided to penetrate the movable platen, the rotational platen, and the fixed platen and a cylinder fixedly provided to the fixed platen. The rotational platen is rotated by rotation driving means that is not specified. The movable platen, the rotational platen, and the fixed platen after mold closing are mold-clamped by a mold clamping cylinder composed of a large-diameter hydraulic cylinder incorporated in the fixed platen and a ram that is slidable in the cylinder. The ram having a large diameter has a function detachable from the tie bar.
The molding effects achieved by this injection molding machine are: drawing the rotational platen by the specific hydraulic cylinder toward the fixed platen side, moving the movable platen for mold closing toward the fixed platen side by the hydraulic cylinder provided between an end of the tie bar and the fixed platen, clamping both the movable platen and the rotational platen by the mold clamping cylinder to boost the pressure of hydraulic oil, injection-molding one resin material from one injection unit into the primary side cavity, rotating the rotational platen 180 degrees to clamp both the movable platen and the rotational platen again, and injecting the other resin material from the other injection unit into the secondary side cavity, whereby the two materials are integrally molded.
A conventional multi-material injection molding machine described in Patent Document 2 is a molding machine that produces a multi-material molding by using molds composed of a fixed mold, a movable mold, and a rotational mold rotating between the fixed mold and the movable mold. The machine includes a first injection machine that injects a molten material into the fixed mold, a second injection machine that injects a molten material into the movable mold, a rotational mold supporting device that supports the rotational mold rotatably and movably toward the movable mold side with a fixed platen, and pressure-clamping means for pressure-clamping the fixed mold and the movable mold through the rotational mold.
The molding effects achieved by this injection molding machine are almost the same as those achieved by the injection molding machine in Patent Document 1.
[Patent Document 1] Japanese Patent Examined Publication No. H3-51207 (FIG. 1)
[Patent Document 2] Japanese Patent Application Laid-open No. 2006-168223 (FIG. 1)